JPH0727021Y2 - Thread trimming device for lockstitch sewing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a thread trimming device for cutting an upper thread and a lower thread below a needle plate in a lockstitch sewing machine.

[Prior Art] Currently, a lockstitch sewing machine is provided with a thread trimming device that automatically performs a thread trimming operation after sewing is completed.
As this thread trimming device, the needle and the sewing machine hook perform a single sewing operation in response to a predetermined thread trimming command, and the movable blade moves horizontally between the needle plate and the sewing machine hook during that time, and the upper thread that passes through the sewing machine hook. It is generally known that a loop and a bobbin thread are caught and cut between a fixed blade. Usually, such a thread trimming device is provided with a leaf spring which is in contact with the blade portion of the movable blade at the initial position of the reciprocating movement of the movable blade, and the end portion of the cut yarn is movable with the leaf spring. By sandwiching the needle thread with the blade, the lower thread can be reliably knotted with the upper thread loop in the next sewing.

[Problems to be Solved by the Invention] However, the above-described conventional thread cutting device has the following problems.

That is, (a) the upper thread and the lower thread are caught at the same position on the movable blade, that is, by the hook-shaped thread catching portion provided at the tip of the movable blade, and cut at the same position with the fixed blade at the same time. It will be. Therefore, not only the lower thread but also the upper thread (hereinafter, this thread is referred to as the needle-side upper thread) connected to the needle has its cut end held by the leaf spring.
Therefore, if the sewn product is taken out after the sewing operation is completed, the needle thread connected to the needle will not easily come out of the sewn product, and the thread will not be fed from the needle thread supply source together with the sewn product. Interfere with.

(B) When the thread trimming operation is performed when the sewing product is not on the needle drop on the needle plate (hereinafter, this thread trimming operation is referred to as drop trimming), the behavior of the upper loop near the needle plate is unstable. Therefore, the thread length from the cutting end of the needle side needle thread held by the leaf spring after cutting to the needle thread insertion hole of the needle becomes irregular, and in some cases due to the lack of thread length, the thread length is increased during the next sewing. The thread may slip out of the needle insertion hole, resulting in poor sewing.

(C) It is desirable that a certain amount of tension be applied to the thread captured by the movable blade during cutting,
When the needle thread passes through the sewing machine hook, the needle thread is fed out from the needle thread supply source to the lower side of the needle plate, so that tension is unlikely to be generated during cutting, and good sharpness cannot be obtained.

This invention was made in view of the above problems, and when taking out the sewn product after thread cutting, the needle side upper thread can be smoothly pulled out from the sewn product, and the needle at the start of the next sewing operation is also performed. It is possible to prevent the upper thread from coming out of the
Moreover, it is an object of the present invention to provide a thread trimming device for a lockstitch sewing machine that can obtain a good sharpness for the upper thread.

[Means for Solving the Problem] The present invention moves a movable blade back and forth once across a needle drop extension line in response to a predetermined thread trimming command, and also performs one sewing operation by a needle of a lock stitch sewing machine and a sewing machine hook. By doing so, the bobbin thread and the upper thread loop are captured by the movable blade, and both threads are cut between the movable blade and the fixed blade that is in sliding contact with the movable blade, and at the same time, the cut both thread ends are moved to the movable blade and the plate. In a thread trimming device for a lockstitch sewing machine, which is sandwiched between a spring and a spring, a non-contact portion with a needle thread loop is formed on a needle thread loop contact surface of a bobbin case mounted in the sewing machine hook, An upper thread withdrawing member having a hook-shaped thread hooking portion that can be fitted into the non-contact portion at a tip end thereof is interlocked with the reciprocating motion of the movable blade and extends from a side of the sewing machine hook to a fitting position with the non-contact portion. Reciprocating motion and moving the movable blade forward and backward. In synchronism with the end of the returning operation, the thread wiping member is moved across the upper thread path from the movable blade to the needle.

[Operation] In this invention, the needle thread withdrawing member reciprocates in conjunction with the reciprocating movement of the movable blade to capture the needle thread loop passing through the front surface of the bobbin case and pull it out to the side of the sewing machine hook. Therefore, the upper thread loop is captured by the movable blade and the upper thread drawing member, and the upper thread path from the movable blade to the needle is bent by the upper thread drawing member at the time of cutting. Therefore, it is possible to increase the length of the upper thread path as compared with the conventional device which does not include the upper thread drawing member, and the upper thread does not come out from the needle thread insertion hole of the needle even when the needle thread is cut off. . Further, since tension is generated in the upper thread by the upper thread drawing operation of the upper thread drawing member, the sharpness corresponding to the upper thread becomes extremely good.

Further, the cut end of the needle side upper thread is once held by the leaf spring at the same time as the cutting operation, but immediately thereafter, the thread wiping member moves across the upper thread path from the movable blade to the needle, and the upper thread drawing member In order to pull off the needle side upper thread pulled out by the thread hooking section, the cut end portion of the thread is pulled out from the leaf spring and becomes in the open state. Therefore, when the sewn product is taken out, the needle-side upper thread does not come out of the sewn product smoothly and unnecessary upper thread is not fed out from the upper thread supply source.
The next sewing operation can be started smoothly.

[Embodiment of the Invention] An embodiment of the invention will be described below with reference to the drawings.

In FIGS. 1 to 3, reference numeral 1 denotes a known sewing machine hook provided below the needle plate B, which is rotatable with respect to an inner hook 2 which is locked to the machine frame of the sewing machine and a peripheral surface of the inner hook 2. A bobbin case 4 having a lower thread bobbin accommodated therein is attached to the inner hook 2. A long groove 4a is formed on the front surface of the bobbin case 4 as a non-contact portion with the upper thread loop.

Reference numeral 6 denotes a thread cutting base fixed to the lower surface of the sewing machine bed, and 7 denotes a moving base movably fitted in a guide groove 6a formed in the thread cutting base 6. This moving base 7 is always in the initial position shown in FIG. 2, and when a predetermined thread cutting command is input, it is connected to the lower shaft of the sewing machine through an interlocking mechanism such as the link member 5 (not shown). While the lower shaft of the sewing machine is positionally rotated together with the upper shaft of the sewing machine, the reciprocating motion is performed along the guide groove 6a by the interlocking mechanism having the rotational force as a driving force. Further, 8 is a plate-shaped movable blade fixed to the upper surface of the moving table 7 with a screw 9, and a hook-shaped thread catching portion 8a is formed at the tip thereof, and further, a blade is provided on the upper surface of the thread catching portion 8a. The portion 8b is formed. Reference numeral 10 is a plate-shaped fixed blade fixed to the upper surface of the front end portion of the thread cutting base 6 with a screw 11, and a blade portion 10a joined to the blade portion 8b of the movable blade 8 is formed at the tip portion thereof. Reference numeral 12 is a leaf spring whose rear end is fixed to the lower surface of the movable table 7 with a screw 13, and its front end is shown.
12a is in pressure contact with the lower surface of the movable blade 8.

Reference numeral 14 is a picker moving base fixed to the lower surface of the moving base 7 with a screw 15, and 16 is a picker fixed to the lower surface of the picker moving base 14 with a screw 15. The tip end of the picker is fixed to the long groove 4a of the bobbin case 4. A thread hooking portion 16a that can be inserted is formed.

A rotary solenoid 18 is attached to the machine frame by a support 19. In this rotary solenoid 18, the solenoid shaft 18a makes one swing rotation in synchronization with the end of the reciprocating motion of the movable blade 8. 20
Is a swing arm whose one end is fixed to the solenoid shaft 18a, and 21 is a wiper (thread wiper member) fixed to the other end of the swing arm 20. And swings integrally with the swing arm 20, and its tip 21a crosses the needle thread path from the movable blade 8 to the needle N between the picker 16 and the sewing machine hook 1.

Next, the operation will be described based on the above configuration.

In the initial state before inputting the thread trimming command, the movable table 7 is located rearward (rightward in FIG. 2), and the thread hooking portion of the movable blade 8
8a is held at a contact position between the fixed blade 10 and the leaf spring 12, that is, at a position retracted from the extension line L of the needle drop position. At this time, the picker 16 has its thread hooking portion 8a located on the side of the sewing machine hook 1, and the wiper 21 has its tip portion 21a at the picker 1a.
Evacuated from route 6 Since the sewing operation is performed in this state, the movable blade 8 and the picker 16 do not interfere with the sewing operation of the needle N and the sewing machine hook 1.

Here, when a thread trimming command is input along with the end of the sewing operation, the sewing machine performs one rotation of the upper shaft and the lower shaft, one sewing operation is performed by the needle N and the outer hook 3, and the movable table 7 is guided. The movable blade 8 and the picker 16 are reciprocated by reciprocating once along the groove 6a. At this time, the movable blade 8 and the picker 16 reciprocate as shown in FIGS. 4 (a) to 4 (f).

That is, the movable blade 8 moves horizontally from the initial position shown in FIG. 4A as shown in FIG.
And the sewing machine hook 1 to cross the extension line L at the needle drop position. At this time, the tip of the movable blade 8 is caught by the sword tip 3a of the outer hook 3 and enters the upper thread loop I1 passing through the inner hook 2, and the two loop threads I1 ₁ and I1 of the loop I1 are caught. Select ₂ as shown in Fig. 4 (c). After that, the movable blade 8
Reaches the most forward movement position and starts returning, and when returning a little, the previously selected loop yarn I11 and bobbin yarn I2 are caught by the yarn catching portion 8a, and both yarns I11 and I2 are pulled out. It moves back toward the initial position (see FIG. 4 (d)). Immediately before the movable blade 8 reaches the initial position, the captured both threads I11, I2
Is cut between the blade portion 8b of the movable blade 8 and the blade portion 10a of the fixed blade 10. As a result, the bobbin thread I2 is divided into a portion connected to the sewing machine hook 1 (hook side lower thread) I2a and a part connected to the sewn product (seam side bobbin thread) I2b, and the upper thread I1 is connected to the needle N ( Needle side upper thread) I1a and the part that continues to the sewn product (Stitch side upper thread) I
Divided into 1b. When the movable blade 8 is completely returned to the initial position, the cut ends of the needle side upper thread I1a and the shuttle side lower thread I2a are clamped between the leaf spring 16 and the movable blade 8.

On the other hand, the picker 16 starts the forward movement together with the movable blade 8 from the initial position shown in FIG. 4 (a), and when it moves a predetermined distance, as shown in FIG. 4 (b), as shown in FIG. Fits into the long groove 4a formed on the front surface of the bobbin case 4, and thereafter moves forward along the long groove 4a. Then, among the upper yarns passing through the inner hook 2, the loop yarn I11 that moves on the front surface side of the bobbin case 4 comes into contact with and is locked by the yarn hooking portion 16a (see FIG. 4 (c)). When I11 comes out of the inner hook 2, it is caught by the thread hooking portion 16a as shown in FIG. 4 (d). Then, the picker 16 moves back together with the movable blade 8 while holding the upper thread loop I1, and when the movable blade 8 cuts the thread, the upper thread loop I1 is pulled out to the side of the sewing machine hook 1 (fourth
(See FIG. (E)). As a result, the upper thread path from the movable blade 8 to the needle N is, as shown in FIG.
The path becomes a bend at 16a, and the path length can be increased as compared with the conventional path without the picker 16 (shown by the one-dot chain line in FIG. 5). Therefore, the length from the needle thread insertion hole Na of the needle N to the needle thread cutting end portion is required even if the thread trimming operation is performed with the temporary sewing material removed (even if the trimming is performed). Since the length is maintained at a sufficient length, the upper thread I1a will not be pulled out from the upper thread insertion hole Na of the needle N in the next sewing.

Further, by increasing the path length of the upper thread loop I1 by the picker 16 as described above, tension is generated in the upper thread loop at the time of cutting, so that good sharpness can be obtained.

At the same time as the cutting operation, the cutting end of the needle side upper thread I1a is
It is once held by the leaf spring 12 together with the shuttle side lower thread I2a.
However, when the returning operation of the movable blade 8 is completed, the solenoid shaft 18a of the rotary solenoid 18 is moved to the sixth position in synchronization with this.
As the wiper 21 rotates in the direction of the arrow A in the figure and its tip 21a crosses the needle thread path from the picker 16 to the needle N, the needle side needle thread I1a is caught by this wiper tip 21a and pulled out. Be done. As a result, the cut end portion of the needle side upper thread I1a held by the leaf spring 12 is pulled away from the leaf spring 12 by the pulling-out operation of the wiper 21, and becomes an open state as shown by the one-dot chain line in FIG. . Therefore, when the sewn product W is taken out, the needle side upper thread I1a is smoothly removed from the sewn product W. Therefore, when the needle thread is taken out, the upper thread is not unnecessarily paid out from the upper thread supply source, and the next sewing operation is not hindered. After the upper thread I1a is pulled off, the wiper 21 is returned to the initial position by the rotary solenoid 18.

By the way, in the above embodiment, the long groove 4a is provided on the front surface of the bobbin case 4 to form the non-contact portion with the needle thread loop I1. However, the non-contact portion is not limited to the long groove 4a, but may be a step portion or It can also be formed by a through hole or the like.

Further, the thread trimming device according to the present invention can be applied to any sewing machine that performs a lock stitching operation, that is, a sewing machine that forms a stitch by knitting an upper thread loop and a lower thread by the cooperation of a needle and a sewing machine hook. The present invention is applicable not only to sewing machines that form straight stitches, but also to sewing machines that perform zigzag stitches.

[Effects of the Invention] As described above, the thread cutting device according to the present invention captures and cuts the upper thread and the lower thread by the reciprocating motion of the movable blade, and draws the upper thread in conjunction with the operation of the movable blade. Since the member reciprocates and catches the upper thread loop passing through the front surface of the bobbin case and pulls it out to the side of the sewing machine hook, the upper thread from the needle to the movable blade at the time of cutting is the upper thread. The length of the path from the upper insertion hole of the needle to the needle thread cutting end should be sufficiently maintained even if the needle is bent because it bends in the drawer member and the path length increases compared to the conventional device. Since the upper thread can be prevented from being pulled out from the needle in the next sewing, the next sewing operation can be reliably performed.

Further, since the upper thread withdrawing member increases the path length of the upper thread loop, tension is generated in the upper thread captured by the movable blade at the time of cutting, and the sharpness at the time of cutting becomes extremely good.

Further, in the thread trimming device according to the present invention, in synchronization with the completion of the returning operation of the movable blade, the thread wiping member traverses the upper thread path from the movable blade to the needle and pulls out the upper thread located in the same path to draw the upper thread. Since the cutting end of the sewing machine is pulled out from the leaf spring, the needle thread cutting end can be smoothly pulled out from the sewn product when the sewn product is taken out, and the sewn product can be taken out without difficulty and unnecessary There is also an effect that the yarn can be prevented from being paid out from the upper yarn supply source.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of the present invention, FIG. 2 (a) is a plan view showing a mounting state of a movable blade, a fixed blade, a leaf spring and a picker in the same embodiment, and FIG. Is a side view of what is shown in FIG. 4A, and FIG.
FIG. 3 is a bottom view of what is shown in FIG. 3, FIG. 3 is an enlarged perspective view of an essential part in the same embodiment, and FIGS. 4 (a) to 4 (f) are explanatory perspective views showing the operating states of the movable blade and the picker in the same embodiment. FIG. 5 is an explanatory side view showing a state when the upper thread is cut in the same embodiment, and FIG. 6 is a perspective view showing an operating state of the wiper in the same embodiment. In the figure, 1 ... Sewing machine hook 4 ... Bobbin case 4a ... Long groove 8 ... Movable blade 8b ... Blade portion 10 ... Fixed blade 10a ... Blade portion 16 ... Picker (needle thread drawing member) 16a. Thread hooking section I1 …… Upper thread loop L …… Extension line for needle drop position 21 …… Wiper (thread wiper)

Claims (1)

[Scope of utility model registration request] 1. An intermediate position between the needle plate and the sewing machine hook,
Fixed with a movable blade that moves in a reciprocating path that crosses an extension line of the needle drop position from an initial position that is horizontally retracted from the drop position of the needle, and a blade portion that is in sliding contact with the blade portion of the movable blade at the initial position A blade and a leaf spring joined to one surface of the movable blade are provided, and the movable blade is reciprocated in position in response to a predetermined thread cutting command, and a stitch forming operation is performed by the needle of the lockstitch sewing machine and the sewing machine hook. By doing this, the lower thread and the upper thread loop formed on the lower surface of the needle plate are caught by the movable blade, and both threads are cut between the movable blade and the leaf spring, and at the same time, the both thread ends cut are set as the movable blade. A thread trimming device for a lockstitch sewing machine that is clamped between a leaf spring and a leaf spring, wherein a non-contact portion with a needle thread loop is formed on the front surface of a bobbin case mounted in the sewing machine hook, and Hook shape that can be inserted into the step An upper thread withdrawing member having a hooking portion, the thread hooking portion reciprocatingly interlocking with the reciprocating movement of the movable blade from a side of the sewing machine hook to a fitting position into the non-contact portion; An upper thread loop passing through the front surface of the case is captured by the thread hooking portion fitted in the non-contact portion, and the captured upper thread loop is pulled out to the side of the sewing machine hook by the return movement of the thread hooking portion, and Provided with a thread wiping member that moves so as to cross an upper thread path from the movable blade to the needle in synchronization with the completion of the returning operation of the movable blade, and the upper thread drawn out by the thread hooking portion of the upper thread drawing member. A thread trimming device for a lockstitch sewing machine, characterized in that the thread is removed by the thread sweeping member.